Reversal of drug-resistance of leukemia K562/ADM cells to chemotherapeutical agents by small interfering RNA

OBJECTIVE:To explore the effect of small interfering RNA(siRNA) on reversing multidrug-resistant leukemia cells. METHODS: Human multidrug-resistant leukemia cell line K562/ADM overexpressing mdr1 gene was used as the target cells. Four siRNAs speciafically targeting mdr1 gene were chemically synthesized and transfected into K562/ADM cells with RNAi-Mate. The silencing efficiency of siRNAs were evaluated by the inhibition of mdr1 mRNA expression measured with RT-PCR and Real-time PCR,and the inhibition of P-glycoprotein (P-gp) expression with flow cytometry (FCM). The sensitivity of the cells to adriamycin (ADM),daunorubicin (DNR) and etoposide (Vp-16) was detected with a MTT colorimetric assay. RESULTS: The siRNA target to the site 333 of mdr1 mRNA (si-mdr1/333) possessed the best silencing efficiency to the given gene. After transfected with si-mdr1/333,the expression of mdr1 mRNA was reduced by 69% and 63% detected with RT-PCR and Real-time PCR, respectively,and the expression of P-gp was decreased by about 50%. Si-mdr1/333 significantly enhanced the sensitivity of K562/ADM cells to ADM, DNR and Vp-16, and the reversal efficiency was 3.45-folds, 1.70-folds and 2.91-folds, respectively. CONCLUSION: siRNA can speciafically depress the expression of mdr1 gene and its product P-gp in drug-resistant K562/ADM cells and reverse multidrug resistance to chemotherapeutical agents.